We have this every now and then. Mainly with traffic from the middle east. Switching the port to something other than 5060 seems to help most of the time. Every so often we need to go the vpn route. I know that yealink, snim and possibly polycom have vpn clients built into them. ------Original Message------ From: Mark Stevens Sender: NANOG To: nanog@nanog.org Subject: Verizon Wireless LTE/4G and SIP Header Manipulation Sent: Sep 22, 2015 12:03 Hi All, Has anyone seen that something (most likely an alg) on Verizon's LTE/4G network is rewriting SIP headers,in particular From Tag identifiers? We cannot make a SIP call from our cellphones (using cellular data) beyond 30 seconds because the TAGs are rewritten and the destination Asterisk server drops the call because of this. Thanks Mark Regards, Dovid